1. Field of the Invention
The present invention relates in general to a silicon semiconductor crystal having a protective film which is a stable film and easy to remove, and more particularly to a method for manufacturing a silicon semiconductor crystal which features prevention of oxidation of surface of the silicon semiconductor crystal in a process for manufacturing semiconductor devices such as in the utilization of the surface of silicon semiconductor crystals.
It also relates to a method for forming a very thin silicon oxide film on the surface of a silicon semiconductor substrate.
It also relates to a method for manufacturing a high-quality silicon semiconductor crystal thin film.
2. Related Art
A natural oxide film of silicon with a thickness of 1.0-1.5 nm is usually formed on the silicon semiconductor crystal surface. When manufacturing semiconductor devices and such using the silicon semiconductor crystal, it is necessary to expose silicon atoms by completely removing the silicon oxide film and such which is covering the silicon semiconductors crystal surface.
Conventionally, methods which have been used to remove the oxide film formed on the silicon semiconductor crystal surface include a method in which the oxide film is removed by means of etching using an aqueous solution of hydrofluoric acid and such and a method in which the oxide film is removed by reduction in an hydrogen atmosphere at a high temperature, approximately 1,100.degree. C.
In the method in which a silicon semiconductor crystal is cleaned with an aqueous Solution of hydrofluoric acid and rinsed with water to terminate the silicon semiconductor crystal surface with hydrogen atoms, the silicon semiconductor crystal surface is relatively stable against oxidation by air because it is covered or terminated with hydrogen atoms. However, as time goes on the oxidation of the silicon semiconductor crystal surface gradually proceeds and there are many cases where the quality of the semiconductor devices is degraded due to the fact that the next process is not conducted promptly within a few tens of seconds after the hydrogen termination and oxidation occurs before the process of actually using the silicon semiconductor crystal surface, such as growing a silicon semiconductor crystal thin film, takes place.
On the other hand, in the method in which the silicon semiconductor crystal is held in a hydrogen atmosphere at a high temperature of about 1,100.degree. C. for a reducing treatment, there are cases of generation of slip dislocation due to thermal stress and deterioration of the dopant concentration distribution.
Such an oxide film which is formed due to oxidation of silicon by air always has a thickness of approximately 1.0-1.5 nm. However, as the semiconductor devices become more highly integrated, a very thin oxide film with an even thinner thickness of approximately 0.5-0.7 nm will be required in the future. It is impossible to form and maintain a thinner oxide film with the aforementioned conventional methods.